Disk for single-disk magnetic clutches

ABSTRACT

A disk-shaped armature for use in single-disk magnetic friction clutches has a disk-shaped body of iron which carries one or two friction generating facings consisting of sintered metal or metallic gauze impregnated with a synthetic plastic lubricant, such as polytetrafluorethylene. The facings extend beyond the end faces of the body and can form part of relatively thick rings which are recessed into the respective end faces or they may be applied to a single light metal ring which surrounds the body or to discrete light metal rings which are recessed into the respective end faces of the body.

United States Patent 1191 Marti Sept. 25, 11973 [54] K FORSlNGLE-DISKMAGNETKC 3,177,998 4/1965 Rossez 188/251 M CLUTCHES 3,270,8469/1966 Arledter.... 192/107 M 3,390,750 7/1968 Albertson 188/251 MInventor: Willi Hermann Marti, Basel, 3,619,676 11/1971 Kawakami 310/78Switzerland 3,664,472 5 1972 Martini 192/107 M [73] Ass1gnee: DelmoranAG, Basel, Switzerland 3 493 Siege /76 [22] Filed: .Dec. 6, 1971 PrimaryExaminer-R. Skudy [30] Foreign Application Priority Data Dec. 15, 1970Switzerland 18574/70 [52] 'U.S. Cl. 310/78 [51] Int. Cl. H02k 7/10 [58]Field of Search 310/78, 75, 76, 92, 310/96, 100; 192/18 B, 107 M;188/218 XL,

251 R, 251 A, 251 M, 264 B [56] References Cited UNITED STATES PATENTS3,589,485 6/1971 Kajitani... 310/78 2,387,050 10/l945 Bell 310/78 Appl.No.: 205,213

AtlorneyMichael S. Striker [57] ABSTRACT A disk-shaped armature for usein'single-disk magnetic friction clutches has a disk-shaped body of ironwhich carries one or two friction generating facings consisting ofsintered metal or metallic gauze impregnated with a synthetic plasticlubricant, such as polytetrafluorethylene. The facings extend beyond theend faces of the body andcan form part of relatively thick rings whichare recessed into the respective end faces or they 1 may be applied to asingle light metal ring which surrounds the body or to discrete lightmetal rings which are recessed into the respective end faces of thebody.

8 Claims, 4 Drawing Figures DISK FOR SINGLE-DISK MAGNETICCLUTCIIESBACKGROUND OF THE INYENTION one or more rotary parts, such as shafts orthe like. Single-disk magnetic friction clutches can be utilized withadvantage in positioning or adjusting motors, for example, in motors ofthe type shown in FIGS. 1 to 3 of German Pat. No. 1,159,745 and thecorresponding US. Pat. No. 3,174,450.

It is already known to provide a single-disk magnetic friction clutchwith a disk-shaped armature which comprises a disk-shaped body ofmagnetically conductive material and one or more friction generatingfacings which are applied to the end faces of the magneticallyconductive body. As a rule, presently known facings consist ofring-shaped pieces of cork impregnated with oil or a heat-resistantgrease. A drawback of such facings is that they are likely to undergodeformation when the clutch is in use; thus, the thickness of a corkring increases substantially in response to a rise in temperature.Moreover, a cork ring is likely to undergo perma-' nent deformation inresponse to the application of abrupt mechanical stresses. Stillfurther, the wear on a cork ring is quite pronounced so that the widthof air gaps between a facing in the form ofa cork ring and the partagainst which the facing is caused to move in response to energizationof a winding varies as the wear on the facing progresses. A relativelywide air gap is un' desirable when the clutch is to react with littledelay in response to energization of its winding or windings. Stillfurther, a clutch wherein the air gap between the disk* shaped armatureand the part against which the armature must move in response toenergization of a winding is relatively wide must furnish substantialmagnetic forces. Relatively short switching times (i.e., the length ofthe interval which elapses between the energization or deenergization ofa winding and the movement of the facing on a disk-shaped armature intoor from engagement with a driven part and/or into and from engagementwith a driving part) are very important in many machines which employmagnetic friction clutches. In positioning or adjusting motors of thetppe disclosed in the aforementioned German Pat. No. 1,159,745, thequaltiy of the switching action can be expressed and the reciprocalvalue of the product of braking time and the accuracy of braking action.Such quality of the switching action depends to a considerable extent onthe length of time which is required to change the position of adisk-shaped armature.

SUMMARY OF THE INVENTION An object of the invention is to provide adisk-shaped armature, particularly for use in single-disk magneticfriction clutches, which can stand substantial mechanical and/or thermalstresses without appreciable changes in its dimensions, which can standlong periods of use without appreciable wear, and which can be used withadvantage in clutches serving to furnish extremely short switchingtimes.

Another object of the invention is to provide novel and improvedfriction generating facings which can be used in armatures of the justoutlined character and whose useful life, resistance to mechanicaldeformation and resistance to volumetric changes as a function oftemperature changes is much more satisfactory than that of presentlyknown facings.

A further object of the invention is to provide an armature whoseinertia is less than the inertia of presently known armatures and whichcan be provided with one or more facings, depending upon the intendeduse of the clutch which embodies the armature.

An additional object of the invention is to provide a magnetic frictionclutch wherein the width of the air gap between the disk-shaped armatureand the part or parts against which the armature is caused to move inresponse to energization of one or more windings is only a smallfraction of the air gap in presently known magnetic friction clutches,and wherein the width of such air gap remains at least substantiallyunchanged after long periods of use of the armature.

The invention resides in the provision of a diskshaped armature(hereinafter called disk) which can be used with particular advantage insingle-disk magnetic friction clutches. The disk comprises a rotary bodyconsisting of iron or another suitable magnetically conductive material,and at least one friction generating facing which extends beyond onesurface of the mag netically conductive body. The facing comprises ametallic carrier (such as a sintered metal or a metallic gauze) for asynthetic plastic lubricant, such as polytetrafluorethylene, whichpreferably permeates the carrier. For example, the carrier may consistof sintered bronze or bronze gauze and may form a ring which extendsbeyond one end face of a disk-shaped magnetically conductive body. Theringshaped facing may be applied to a light metal ring which is recessedinto the one end face of the body, to a light metal ring which surroundsthe disk-shaped body, or such facing may form part of a relatively thickring which is recessed into the one end face of the body so that only asmall portion thereof extends beyond the respective end face.

, The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved disk itself, however, both as to its construction and its modeof operation, together with additional features and advantages thereof,will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. la is a fragmentary axialsectional view of a disk which embodies one form of the invention;

FIG. lb .is a similar fragmentary axial sectional view of a second disk;

FIG. 2 is a similar fragmentary axial sectional view of a third disk;and

FIG. 3 is an axial sectional view of a single-disk magnetic frictionclutch embodying a disk of the type shown in FIG. llb.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The disk 1 of FIG. comprises anannular diskshaped body 2 of magnetically conductive material,preferably iron, the two end faces of which are provided withring-shaped recesses 2a, 2b for two aluminum rings 3, 4. The peripheralsurfaces of the rings 3,

4 are flush with the peripheral surface of the body 2. The exposedend-faces of the disks 3, 4 are provided with thin ring-shaped frictiongenerating facings 5, 6 which can be glued or otherwise secured to therespective rings. The facings 5, 6 consist of a metallic carrier, forinstance bronze gauze which is permeated with a synthetic plasticlubricant, such as polytetrafluorethylene The width of the facings S, 6as considered in the radial direction of the body 2, preferably equalsthe width of the respective rings 3, 4 and their thickness is intherange ofa small fraction of one millimeter, e.g., 0.1 mm and normallynot more than 0.5 mm. The internal surface of the body 2 is providedwith axially parallel splines 16.

The disk 1A of FIG. lb comprises a body 2 of iron which is also providedwith splines 16 and recesses 2a, and 2b. These recesses receive rings 7,8 which consist of sintered bronze containing polytetrafluorethylene.The thickness of the rings 7, 8 exceeds the depth of the recesses 20, 2bas considered. in the axial direction of the body 2, so that portions ofthe rings 7, 8 extend beyond the respective end faces of the body 2 andconstitute facings analogous to the facings 5, 6 of FIG. la. Forexample, the thickness of those portions of the rings 7, 8 which extendbeyond the respective end faces of the body 2 may be in the range of0.1-0.5 mm. The disk 1A of FIG. lb is simpler and less expensive thanthe disk of FIG. la. On the other hand, the useful life of the disk 1 isnormally longer than that of the disk 1A. Moreover, the overall weightand hence the inertia of thevdisk 1 is less than that of the disk 1Abecause the rings 3, 4 consist of light metal. Low inertia is desirablewhen the disk is used in clutches which are to accelerate or deceleratea rotary component with minimal losses in time.

The disk 18 of FIG. 2 comprises a magnetically conductive annulardisk-shaped body 9 which is surrounded by a ring 10 of aluminum oranother light metal. The ring 10 is secured to the disk body 9 by one ormore keys 100 or analogous connecting means. The end faces of the ring10 are provided with ring-shaped facings 5, 6 which are glued orotherwise securely bonded thereto and which may consist of bronze gauzepermeated with polytetrafluorethylene, the same as the rings 5, 6 ofFIG. la. The weight of the disk 1B is even less than that of the disk 1so that a clutch using the disk 18 can accelerate or arrest a drivencomponent within an extremely short period of time. The peripheralsurfaces of the facings 5, 6 are preferably flush with the peripheralsurface of the light metal ring 10 and their thickness may be in therange of one or more tenths of a millimeter. The internal surface of thedisk body 9 is provided with axially parallel splines, not shown.

FIG. 3 illustrates a single-disk magnetic friction clutch which embodiesthe disk 1A of FIG. lb. This clutch constitutes or forms part of anauxiliary control means for a positioning or adjusting motor of the typedisclosed in German Pat. No. 1,159,745. The auxiliary control means cancompel, by way of a worm shaft 13, a rotary brake disk not shown in FIG.3 of a clutch motor 12 to rotate at a relatively low speed. The wormshaft 13 is journalled in antifriction bearings l4, l5 and its left-handend portion, as viewed in FIG. 3, is provided with splines which matewith the splines 16 of the disk 1A. Thus, the disk [A is free to moveaxially but shares all angular movements of the worm shaft 13.

One end face of the disk 1A is adjacent to a stationary housing member17 which contains a braking winding 18. The other end face of the disk1A is adjacent to a driving member 19 here shown as a pulley whichreceives torque from the motor 12 or from an auxiliary motor (not shown)by way of one or more belts 21. The driving member 19 accommodates awinding 20.

When the winding 18 is energized in a manner not forming part of thepresent invention, the disk 1A is attracted to the housing member 17 andcauses a practically instantaneous stoppage of the worm shaft 13 by wayof the splines 16. If the winding 20 in the driving member 19 isenergized, the disk 1A moves axially in a direction to the right, asviewed in FIG. 3, and is attracted to the member 19 so that the shaft 13is practically instantaneously accelerated to the speed of the member19.

It was found that the facings 5, 6 or the facing formed by theaforediscussed portions of the rings 7, 8 can stand much longer wearthan conventional facings of cork or the like. Moreover, the volumetricchanges of the improved facings in response to changes in temperatureare much less pronounced than those of cork facings, i.e., the swellingof the facings 5, 6 or 7, 8 in response to heating is negligible. Thisfeature, in addition.

to greatly reduced wear, renders it possible to mount the improved diskwith minimal clearance, i.e., with extremely narrow air gaps, to thusreduce the length of time which is necessary to attract the disk to astationary braking or housing member or to a rotary driving member inresponse to energization of the respective winding. Also, the width ofthe selected air gaps varies very little in response to extended use ofthe clutch so that the switching times remain stable for long periods oftime.

The energy which is converted into heat, especially when the improveddisk is caused to engage the braking or housing member 17, can bereadily dissipated because the parts which constitute and/or carry thefacings consist of a metallic material. Moreover, the coefficient offriction of the facings on the improved disk varies very little or notat all when the temperature of the disk changes. Still further, thefacings of the improved disk can stand substantial mechanical stressesor impacts without any appreciable deformation. The selected air gap canbe extremely narrow due to the volumetric stability of the facings andalso because the facings employ a synthetic plastic lubricant in apermeable metallic carrier. The clutch which embodies the improved diskcan operate with relatively small magnetic forces because the width ofthe air gap or gaps can be reduced well below that of air gaps inclutches having disks which are provided with conventional facings.

It is clear that the clutch of FIG. 3 can employ the disk 1 or the disk13 as well as that the disk which is used in the clutch can merely serveto couple the shaft 13 to the braking or housing member 17 or to thedriving member 19. In such clutches, the disk can be provided with asingle facing or only one of the two facings is in actual use whereasthe other facing serves as a spare facing to be put in use afterextensive wear upon the one facing. Also, the facing or facings mayemploy another synthetic plastic material with satisfactory lubricatingcharacteristics.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can,

ous applications without omitting features which fairly t constituteessential characteristics of the generic and specific aspects of mycontribution to the art and,

therefore, such adaptations should and are intended to becomprehendedwithin the meaning and range of equivalence of the claims-What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

l. A disk-shaped armature, particularly for use in single-disk magneticfriction clutches, comprising a rotary disk consisting of magneticallyconductive material and having a pair of end faces, at least one ofwhich is provided with a ring-shaped recess; a light metal ring in saidrecess; and a friction generating facing extending beyond said oneendface of said disk and comprising a metallic carrier for a syntheticplastic lubricant, said facing being supported by said light metal ring.

2. An armature as defined in claim 1, wherein said metallic carrier ispermeated with said lubricant.

g 3. An armature as defined in claim 1, wherein said lubricant ispolytetrafluorethylene.

4. An armature as defined in claim 1, wherein said metallic carrier is asintered metal.

5-.An armature as defined in claim 1, wherein said carrier is a metallicgauze.

6. An armature as defined in claim 1, wherein said carrier consists ofbronze.

7. An armature as defined in claim 1, wherein said facing is-a ringwhich extends slightly beyond said one surface of said disk.

8. A disk-shaped armature, particularly for use in single-disk magneticfriction clutches, comprising a rotary disk having two end faces andconsisting of magnetically conductive material; at least one frictiongenerating facing extending beyond one of said end faces of said disk,said facing comprising a metallic carrier for synthetic plasticlubricant; and a light metal ring surrounding said disk and supportingsaid facing.

1. A disk-shaped armature, particularly for use in single-disk magneticfriction clutches, comprising a rotary disk consisting of magneticallyconductive material and having a pair of end faces, at least one ofwhich is provided with a ring-shaped recess; a light metal ring in saidrecess; and a friction generating facing extending beyond said one endface of said disk and comprising a metallic carrier for a syntheticplastic lubricant, said facing being supported by said light metAl ring.2. An armature as defined in claim 1, wherein said metallic carrier ispermeated with said lubricant.
 3. An armature as defined in claim 1,wherein said lubricant is polytetrafluorethylene.
 4. An armature asdefined in claim 1, wherein said metallic carrier is a sintered metal.5. An armature as defined in claim 1, wherein said carrier is a metallicgauze.
 6. An armature as defined in claim 1, wherein said carrierconsists of bronze.
 7. An armature as defined in claim 1, wherein saidfacing is a ring which extends slightly beyond said one surface of saiddisk.
 8. A disk-shaped armature, particularly for use in single-diskmagnetic friction clutches, comprising a rotary disk having two endfaces and consisting of magnetically conductive material; at least onefriction generating facing extending beyond one of said end faces ofsaid disk, said facing comprising a metallic carrier for syntheticplastic lubricant; and a light metal ring surrounding said disk andsupporting said facing.